D equivalent of C++ reinterpret cast?

[Simen kjaeraas]

Bradley Mitchell <abstractant1 at gmail.com> wrote:

>     int xi = cast(int)cast(void*)x;
[...]
>     x = cast(float)cast(void*)xi;

The simple solution (seeing as how x is an lvalue) is


     int xi = *cast(int*)&x;
[...]
     x = *cast(float*)&xi;

Function version:

T reinterpret( T, U )( U value ) {
     return *cast( T* )&value;
}

There may be situations in which this will not work (though
I know of none, OTOH), and where using a union will:

T reinterpret( T, U )( U value ) {
     union Uni {
         U u;
         T t;
     }
     return Uni(value).t;
}

Of course, these are general solutions, and the easy solution
to your problem is to use a union directly:


float fastInvSqrt( float x ) {
     enum int INV_SQRT_N = 1597292357;
     enum float MULT = 1.000363245811462f;

     float mx = 0.5f * MULT * x;
     union Xu {
         float f;
         int i;
     }
     Xu xu = Xu(x);
     xu.i = INV_SQRT_N - (xu.i >> 1);
     return xu.f * (1.5f * MULT - mx * xu.f * xu.f);
}


-- 
Simen